This invention relates to an implantable anti-reflux fluid displacement compression pump-catheter used to transfer an unwanted accumulation of body fluids from a body cavity to a site where they can be processed by the body. The primary use for the pump-catheter is in the treatment of patients with ascites by the displacement of accumulated peritoneal cavity fluid into the systemic venous circulation.
The word "ascites" comes from the Greek word "askos" for bag. Hippocrates stated: "When the liver is full of fluid and this overflows into the peritoneal cavity so that the belly becomes full of fluid, death follows." Indeed, this is a very accurate description of the mechanism for ascites, as it is known today. There is evidence of the fact that ascites occurs with the obstruction, or increase in pressure, of hepatic lymphatics with a subsequent oozing of lymphatic fluid from the surface of the liver. If the fluid flux is high, especially in an individual with liver disease and portal venous system hypertension, there is inadequate re-absorption of this fluid and it accumulates within the peritoneal cavity.
Ascites pathophysiology, and the exchange of fluid between the peritoneal cavity and the various peritoneal surfaces, follows Starling's hypothesis. The pressure in the portal vein plus the oncotic pressure of the peritoneal fluid is the force that drives fluid from the intravascular space into the peritoneal cavity. This filtration force is opposed by the intraperitoneal hydrostatic pressure plus the plasma oncotic pressure. Since the liver capillaries are freely permeable to protein, any type of pressure imbalance of the above forces in favor of the production of peritoneal fluid leads to the formation of ascites.
In addition to the discomfort and pressure problems associated with massive abdominal distention due to ascites, patients with ascites are more prone to develop reflux esophagitis, respiratory failure, abdominal wall hernia defects, renal failure, and an increased susceptibility to infections.
The most frequent cause of ascites in the United States is cirrhosis of the liver, in 80 to 85% of the cases resulting from chronic alcoholism. According to the last U. S. census, there are believed to be approximately 600,000 ascitic individuals with alcoholic cirrhosis in this country.
In addition, there are other causes of ascites: chylous ascites, nephrogenic ascites, cardiogenic ascites, malignant ascites, and ascites due to other rare conditions. In other parts of the world, in particular in Asia, ascites is more often the result of liver disease due to parasitic infection.
In addition to its use in the management of ascites, the pump-catheter of this invention can, with modest modifications, be utilized for the transfer of other body fluids, e.g. the displacement of brain ventricular fluid in hydrocephalus to either the right atrium of the heart or to the peritoneal cavity.